I have a Crosman Model 66-A1 Powermaster I got from my father in the mid 1970's. The plunger cup failed and I am trying to get the pin out so I can service it. It isn't a roll pin like every single one online, but similar to a rivet with a c-clip. I have attached some pics. I have tried using a hammer and line punch with penetrant and let it sit overnight and it will still not budge. Any help will be greatly appreciated.